/Engine/Source/Runtime/Landscape/Classes/LandscapeComponent.h
Get the physical materials that are configured by the landscape component graphical material. Returns false if there are no non-null physical materials. (We probably don't want to use if no physical material connections are bound.)
bool GetRenderPhysicalMaterials ( [TArray](API\Runtime\Core\Containers\TArray)< [UPhysicalMaterial](API\Runtime\PhysicsCore\PhysicalMaterials\UPhysicalMaterial) * > & OutPhysicalMaterials ) const